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Setting idle speed on ERIC systems
If you want to set the idle speed on your 1.6 or 2.0 Montego fitted with the ERIC (Electronically regulated ignition & carburetion) even better than it left the factory, it is not as straight forward as twiddling the idle screw.
First thing you will need to do is make yourself some simple special tools. You will notice that the screw that you normally adjust the idle speed on the SU HIF44E is different. The reason for the change is this screw is only used for setting a base idle setting. You can make a tool to turn the screw, by taking a cheap old No.2 size screwdriver, saw off the end square and then put a junior hacksaw cut in the middle of the cross section.
To turn the screw that is in a similar position to the old fast idle screw, either a very small socket or the head of an allen screw braised onto an old screw driver, will be easier than messing around with long nose pliers etc. This screw no longer sets the fast idle; it is used to set the controlled idle speed. On ERIC systems it is not necessary to remove the coolant sensor plug to make any carburettor adjustments.
Lastly you will need a dummy electrical plug to fool the ECU. This was originally a Rover special tool 18G 1560 but with a little imagination you can make one.
The best way is to cut a similar plug from an old wiring loom but failing that you can use the one on your own car that is protecting the ECU serial port connection, as long as you find an alternative method to protect the plug from dirt and moisture. The ECU serial port diagnostic plug is in the under bonnet harness between the bulkhead and the ERIC ECU on the N/S inner wing. The plug cover has three black wires and is just taped into the loom to secure it, after disconnecting it from the serial port connection usually a good tug will remove it from the loom. Cut and bare all the wires then join wires A and B (see diagram) leaving the wires exposed then attach a small crocodile clip to wire C, and that is job done. 
Before you begin tuning the engine it should be in good mechanical condition with correct valve clearances etc. and you should carry out the usual checks for air leaks or blockages in vacuum hoses and breather hoses, air filter and ignition components are in good condition, inlet air temp control components are working correctly, and the engine & transmission are at full operating temperature with all electrical loads off (i.e. lights, HRW, radio, heater fan, cooling fan etc.).
Connect dummy plug with A, B & C joined, into the serial diagnostic connection on vehicle harness, using the base idle screw (old idle screw) set the base idle speed to 625rpm +/- 25rpm, at this point check there is at least 6mm deflection (free play) in throttle cable. Once the base idle is set remove dummy plug and connect the wires A & B only, then refit dummy plug and using the controlled idle speed adjusting screw (old fast idle screw position) set the controlled idle speed to 750 – 800 rpm. Remove dummy plug hold engine speed at 2000 rpm for 20 seconds then allow to idle and check and adjust the CO to 2.5% +/- 0.5%. Once the CO is set recheck base idle and controlled idle. If cooling fan cuts in stop tuning until fan cuts out, then raise engine speed to 2000 rpm for 20 seconds return to idle and continue.
Obviously to set the CO the only accurate way is to use a gas analyser, but with careful practice it is possible to get the CO mixture somewhere close by ear. Disconnect the stepper motor plug, slowly turn the CO adjusting screw anticlockwise until engine speed drops and stumbles, screw the CO screw clockwise until engine runs its fastest. Then turn CO screw anticlockwise until engine speed just slows slightly (turn screw very slowly and listen to engine note carefully). Then turn CO screw clockwise no more than half a turn from this point to achieve the smoothest fastest idle speed. Reconnect the stepper motor plug.
Regards Gary
First thing you will need to do is make yourself some simple special tools. You will notice that the screw that you normally adjust the idle speed on the SU HIF44E is different. The reason for the change is this screw is only used for setting a base idle setting. You can make a tool to turn the screw, by taking a cheap old No.2 size screwdriver, saw off the end square and then put a junior hacksaw cut in the middle of the cross section.
To turn the screw that is in a similar position to the old fast idle screw, either a very small socket or the head of an allen screw braised onto an old screw driver, will be easier than messing around with long nose pliers etc. This screw no longer sets the fast idle; it is used to set the controlled idle speed. On ERIC systems it is not necessary to remove the coolant sensor plug to make any carburettor adjustments.
Lastly you will need a dummy electrical plug to fool the ECU. This was originally a Rover special tool 18G 1560 but with a little imagination you can make one.
The best way is to cut a similar plug from an old wiring loom but failing that you can use the one on your own car that is protecting the ECU serial port connection, as long as you find an alternative method to protect the plug from dirt and moisture. The ECU serial port diagnostic plug is in the under bonnet harness between the bulkhead and the ERIC ECU on the N/S inner wing. The plug cover has three black wires and is just taped into the loom to secure it, after disconnecting it from the serial port connection usually a good tug will remove it from the loom. Cut and bare all the wires then join wires A and B (see diagram) leaving the wires exposed then attach a small crocodile clip to wire C, and that is job done. Before you begin tuning the engine it should be in good mechanical condition with correct valve clearances etc. and you should carry out the usual checks for air leaks or blockages in vacuum hoses and breather hoses, air filter and ignition components are in good condition, inlet air temp control components are working correctly, and the engine & transmission are at full operating temperature with all electrical loads off (i.e. lights, HRW, radio, heater fan, cooling fan etc.).
Connect dummy plug with A, B & C joined, into the serial diagnostic connection on vehicle harness, using the base idle screw (old idle screw) set the base idle speed to 625rpm +/- 25rpm, at this point check there is at least 6mm deflection (free play) in throttle cable. Once the base idle is set remove dummy plug and connect the wires A & B only, then refit dummy plug and using the controlled idle speed adjusting screw (old fast idle screw position) set the controlled idle speed to 750 – 800 rpm. Remove dummy plug hold engine speed at 2000 rpm for 20 seconds then allow to idle and check and adjust the CO to 2.5% +/- 0.5%. Once the CO is set recheck base idle and controlled idle. If cooling fan cuts in stop tuning until fan cuts out, then raise engine speed to 2000 rpm for 20 seconds return to idle and continue.
Obviously to set the CO the only accurate way is to use a gas analyser, but with careful practice it is possible to get the CO mixture somewhere close by ear. Disconnect the stepper motor plug, slowly turn the CO adjusting screw anticlockwise until engine speed drops and stumbles, screw the CO screw clockwise until engine runs its fastest. Then turn CO screw anticlockwise until engine speed just slows slightly (turn screw very slowly and listen to engine note carefully). Then turn CO screw clockwise no more than half a turn from this point to achieve the smoothest fastest idle speed. Reconnect the stepper motor plug.
Regards Gary
Attached Files